As for oil well cements used for cementing of shaft wall, there are extremely strict requirements on their indexes of physical and mechanical properties, such as cement thickening time. It's also explicitly formulated in National Standards for oil well cements that the cement thickening time should be tested by a pressurized consistometer.
Presently, most of the methods for measuring cement consistency for a consistometer at home and abroad are implemented according to a measuring method by the consistometer of US Chandler Engineering Company, i.e. providing a potentiometer inside a pressure vessel of a consistometer for measuring cement consistency. However, this method has the following problems:
1. Lacking high measurement accuracy. The measurement accuracy is directly affected by contact pressure of a sliding contact arm of the potentiometer, surface finish of a resistance sheet and quality of bearings. The bad conditions inside pressure vessel, such as high temperature, high pressure, high pollution and high corrosion, also cause the technical index of the potentiometer that has already been adjusted decrease quickly. A gross error is inevitably produced and an incorrect value is shown directly sometimes.
2. The potentiometer having too many wearing components requiring a regular repair and correction, which, however, is rather difficult.
These deficiencies described above limit the improvement of the technical index of the conventional potentiometer measuring method.